A gas line explosion on Thursday night at John F. Kennedy High School in New York City left three people injured and destroyed three floors of the school building, the New York City Police Department and Mayor Bill de Blasio reported, according to USA Today.

The three victims, who are construction workers, were seriously hurt and are being treated at Jacobi Medical Center, de Balsio said. New York officials say that blast was "very serious" and caused severe burns on the victims.

The explosion happened at around 8 p.m. EDT during construction work in the school's sixth-floor laboratory. The blast immediately destroyed two non-load-bearing walls, a police spokesperson stated, according to Reuters.

"This school obviously has sustained some very, very serious damage," de Blasio said at the scene. "This was part of a project being run by the school construction authority through a private contractor."

Located on the western edge of Marble Hill, politically on the side of Manhattan, the high school is still identified geographically and by the Department of Education as in the Bronx.

The neighbors were terrified.

"The room I was in shook. The whole room shook," said Emily Langer of Marble Hill. "You feel that, 'Oh my God.' We went outside. And our neighbors were like, 'Oh my God, did you feel that? What was that?' And then right away, we heard the sirens."

"There's contractors up there. They're working up there. So they're working up there - I think they're making them do a few classrooms or something like that; chemistry room. And it just broke down when they hit it with a blow torch, and that was it," said a custodian who was working when the explosion happened, CBS New York reported.

"For people in this community, obviously this was a real shock," de Blasio said. "Our hearts go out to (the injured construction workers) and their families."